<?php
/**
 * MacBinary signature checker and data fork extractor, for files
 * uploaded from Internet Explorer for Mac.
 *
 * Copyright (C) 2005 Brion Vibber <brion@pobox.com>
 * Portions based on Convert::BinHex by Eryq et al
 * http://www.mediawiki.org/
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @ingroup SpecialPage
 */

class MacBinary
{
  protected
    $handle,
    $valid,
    $version,
    $filename,
    $dataLength,
    $resourceLength;
    
  public function __construct($filename)
  {
    $this->valid          = false;
    $this->version        = 0;
    $this->filename       = '';
    $this->dataLength     = 0;
    $this->resourceLength = 0;
    
    $this->open($filename);
    $this->loadHeader();
  }

  /**
   * The file must be seekable, such as local filesystem.
   * Remote URLs probably won't work.
   *
   * @param string $filename
   */
  public function open($filename)
  {
    $this->handle = fopen($filename, 'rb');
  }

  /**
   * Does this appear to be a valid MacBinary archive?
   * @return bool
   */
  public function isValid()
  {
    return $this->valid;
  }

  /**
   * Get length of data fork
   * @return int
   */
  public function dataForkLength()
  {
    return $this->dataLength;
  }

  /**
   * Copy the data fork to an external file or resource.
   * @param resource $destination
   * @return bool
   */
  public function extractData($destination)
  {
    if(!$this->isValid())
    {
      return false;
    }

    // Data fork appears immediately after header
    fseek($this->handle, 128);
    return $this->copyBytesTo($destination, $this->dataLength);
  }

  /**
   *
   */
  public function close()
  {
    fclose($this->handle);
  }

  // --------------------------------------------------------------

  /**
   * Check if the given file appears to be MacBinary-encoded,
   * as Internet Explorer on Mac OS may provide for unknown types.
   * http://www.lazerware.com/formats/macbinary/macbinary_iii.html
   * If ok, load header data.
   *
   * @return bool
   * @access private
   */
  public function loadHeader()
  {
    $fname = 'MacBinary::loadHeader';

    fseek($this->handle, 0);
    $head = fread($this->handle, 128);
    #$this->hexdump( $head );
    
    if (strlen($head) < 128)
    {
      //wfDebug( "$fname: couldn't read full MacBinary header\n" );
      return false;
    }

    if ($head{0} != "\x00" || $head{74} != "\x00")
    {
      //wfDebug( "$fname: header bytes 0 and 74 not null\n" );
      return false;
    }

    $signature     = substr($head, 102, 4);
    $a             = unpack("ncrc", substr($head, 124, 2));
    $storedCRC     = $a['crc'];
    $calculatedCRC = $this->calcCRC(substr($head, 0, 124));
    
    if ($storedCRC == $calculatedCRC)
    {
      $this->version = ($signature == 'mBIN') ? 3 : 2;
    }
    else
    {
      $crc = sprintf("%x != %x", $storedCRC, $calculatedCRC);
      if 
      (
        $storedCRC == 0 && 
        $head{82} == "\x00" && 
        substr( $head, 101, 24 ) == str_repeat("\x00", 24)
      )
      {
        //wfDebug( "$fname: no CRC, looks like MacBinary I\n" );
        $this->version = 1;
      }
      elseif ($signature == 'mBIN' && $storedCRC == 0x185)
      {
        // Mac IE 5.0 seems to insert this value in the CRC field.
        // 5.2.3 works correctly; don't know about other versions.
        //wfDebug( "$fname: CRC doesn't match ($crc), looks like Mac IE 5.0\n" );
        $this->version = 3;
      }
      else
      {
        //wfDebug( "$fname: CRC doesn't match ($crc) and not MacBinary I\n" );
        return false;
      }
    }

    $nameLength = ord( $head{1} );
    if ($nameLength < 1 || $nameLength > 63)
    {
      //wfDebug( "$fname: invalid filename size $nameLength\n" );
      return false;
    }
    $this->filename = substr($head, 2, $nameLength);

    $forks                = unpack("Ndata/Nresource", substr($head, 83, 8));
    $this->dataLength     = $forks['data'];
    $this->resourceLength = $forks['resource'];
    $maxForkLength        = 0x7fffff;

    if ($this->dataLength < 0 || $this->dataLength > $maxForkLength)
    {
      //wfDebug( "$fname: invalid data fork length $this->dataLength\n" );
      return false;
    }

    if ($this->resourceLength < 0 || $this->resourceLength > $maxForkLength)
    {
      //wfDebug( "$fname: invalid resource fork size $this->resourceLength\n" );
      return false;
    }

    //wfDebug( "$fname: appears to be MacBinary $this->version, data length $this->dataLength\n" );
    $this->valid = true;
    return true;
  }

  /**
   * Calculate a 16-bit CRC value as for MacBinary headers.
   * Adapted from perl5 Convert::BinHex by Eryq,
   * based on the mcvert utility (Doug Moore, April '87),
   * with magic array thingy by Jim Van Verth.
   * http://search.cpan.org/~eryq/Convert-BinHex-1.119/lib/Convert/BinHex.pm
   *
   * @param string $data
   * @param int $seed
   * @return int
   * @access private
   */
  public function calcCRC($data, $seed = 0)
  {
    # An array useful for CRC calculations that use 0x1021 as the "seed":
    $MAGIC = array(
      0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7,
      0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef,
      0x1231, 0x0210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6,
      0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de,
      0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485,
      0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d,
      0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4,
      0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc,
      0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823,
      0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b,
      0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50, 0x3a33, 0x2a12,
      0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a,
      0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41,
      0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49,
      0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70,
      0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78,
      0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f,
      0x1080, 0x00a1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067,
      0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e,
      0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256,
      0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d,
      0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
      0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c,
      0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634,
      0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab,
      0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3,
      0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a,
      0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92,
      0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9,
      0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1,
      0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8,
      0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0
    );
    $len = strlen($data);
    $crc = $seed;
    for ($i = 0; $i < $len; $i++)
    {
      $crc ^= ord($data{$i}) << 8;
      $crc &= 0xFFFF;
      $crc = ($crc << 8) ^ $MAGIC[$crc >> 8];
      $crc &= 0xFFFF;
    }
    return $crc;
  }

  /**
   * @param resource $destination
   * @param int $bytesToCopy
   * @return bool
   * @access private
   */
  public function copyBytesTo($destination, $bytesToCopy)
  {
    $bufferSize = 65536;
    for ($remaining = $bytesToCopy; $remaining > 0; $remaining -= $bufferSize)
    {
      $thisChunkSize = min($remaining, $bufferSize);
      $buffer        = fread($this->handle, $thisChunkSize);
      fwrite($destination, $buffer);
    }
  }
}
